Machine-based, i.e. automated, systems capable of tracking musical scores cannot "listen" and react to musical performance deviations in the same way as a human musician. A trained human musician listening to a musical performance can follow a corresponding musical score to determine, at any instant, the performance location in the score, the tempo (speed) of the performance, and the volume level of the performance. The musician uses this information for many purposes, e.g., to perform a synchronized accompaniment of the performance, to turn pages for the performer, or to comment on the performance.
However, machine-based score tracking is useful because it is often difficult to practice a musical piece requiring the participation of a number of different musical artists. For example, a pianist practicing a piano concerto may find it difficult to arrange to have even a minimal number of musical artists available whenever he or she desires to practice. Although the musical artist could play along with a prerecorded arrangement of the musical piece, the artist may find it difficult to keep up with the required tempo while learning the piece. Also, the performer is restrained from deviating, from the prerecorded arrangement, for expressive purposes. For example, if the performer changes tempo or volume, the prerecorded arrangement does not vary in speed or volume to match the performance. Further, it is often tedious to search an entire prerecorded piece of music for the particular segment of the work requiring practice.
Accordingly, there is a need for an automated system which can track a musical score in the same manner, i.e. correlating an input performance event with a particular location in an associated musical score. This allows a musician to perform a particular musical piece while the system: (i) provides a coordinated audio accompaniment; (ii) changes the musical expression of the musician's piece, or of the accompaniment, at predetermined points in the musical score; (iii) provides a nonaudio accompaniment to the musician's performance, such as automatically displaying the score to the performer; (iv) changes the manner in which a coordinated accompaniment proceeds in response to input; (v) produces a real-time analysis of the musician's performance; or (vi) corrects the musician's performance before the notes of the performance become audible to the listener.